Thursday, December 31, 2009


Here is the thesis I will argue for: that x intentionally kills y does not entail that x intended that y die.

I need a relevance principle for intentions:

(RPI) If x intends that p in an action A, then x takes the epistemic conditional probability of p on A to be higher than the epistemic conditional probability of p on some relevant alternative (such as refraining from A).

Now suppose that George is falling past Fred's balcony. Under the building there is a net spread out. George's fall is such that he is virtually certain to miss the net unless his path is modified, and it is virtually certain that he'll die if he misses the net. Fred has always wanted to kill George. It's not that Fred has wanted George dead, but Fred wanted to take revenge on George, to be the cause of George's death. Fred has a baseball bat. If he hits George on the head, George's downward path will be modified and George will land on the net. There is no other intervention within Fred's power that can stop George from hitting the ground. If Fred hits George on the head with the bat, George has a 90% chance of dying from the blow, and a 1% chance of dying from landing on the net. Fred knows all this. He hits George on the head, and George dies from the blow.

Fred has intentionally killed George. But by RPI, Fred did not intend George's death, roughly because the action of hitting George with the bat did not increase the conditional (epistemic) probability of George's death.

Clearly, Fred intended that George should die of Fred's blow. Therefore, that one can intend that George die of Fred's blow without intending that George die.

This shows that there isn't going to be any plausible entailment principle for intentions, even if entailment is going to be understood along the lines of any plausible relevant logic (for the entailment from George dying of Fred's blow to George dying had better be relevant). Interestingly, it is not even true that he who intends the conjunction intends the conjuncts. Suppose that if I do nothing, p has probability 0.7 and q has probability 0.7, but the probability of the conjunction is only 0.1. But if I perform A, then p has probability 0.6, as does q, and the conjunction of p and q has probability 0.55. I want the conjunction of p and q, and I don't care about each conjunct (maybe I get a payoff if the conjunction holds, but I get nothing for each conjunct on its own). I know all this. So I perform A. I do not intend p, since I lowered the probability of p. Likewise, I do not intend q. But I do intend their conjunction.

In particular, this implies that in the Principle of Double Effect, the condition that one not intend the evil has to be expanded. Consider this weird case. If a peanut is eaten and Fred is killed, ten innocent people are saved. If the conjunction does not hold, ten innocent people die. Double Effect advocates (like me) will not permit me to wave a magic wand that simultaneously causes Fred to die and the peanut to be eaten (maybe by Fred who is allergic to peanuts?). However, note that Fred's death is not intended here, either as an end or as a means. Only the conjunction of Fred's death and the ingestion of the peanut is intended.

The correct way to expand the condition that one not intend the evil is tricky, and what I sketch in this paper still seems to me to be the best way to go.


Heath White said...

I think you have to be careful between "intentionally" and "intends". What your argument seems to argue for is that even if X intends to kill Y, and succeeds, it does not follow that X intends that Y die. It is also true that if X intends to kill Y, and succeeds, then X has intentionally killed Y. But those two propositions do not combine to yield the proposition that: even if X intentionally kills Y then it does not follow that X intends that Y die.

There is a pretty persuasive logic for intending laid out in Belnap et al, _Facing the Future_, under the label of "seeing to it that," if you care to explore it.

With respect to both Freds, it seems to me there is an easier way out for the DDE theorist. It may be that Fred's death is inevitable or likely, and on this basis a Fred-killer does not intend that Fred die. However, the killing of Fred (by this agent) is not inevitable or likely unless the agent so chooses, so that can be the evil to be avoided.

Alexander R Pruss said...

Well, wait. My argument seems to show that the following are compossible:
1. X intends to kill Y
2. X does not intend that Y die


3. X intentionally kills Y

is entailed by 1. Since 3 is entailed by 1, and 1 and 2 are compossible, likewise 3 and 2 are compossible. But if 3 and 2 are compossible, then: even if X intentionally kills Y (that's what 3 says), it does not follow that X intends that Y die (that's the negation of 2).

I don't think STIT is intending. Belnap et al.'s STIT just doesn't cut finely enough for intending. One can have events E and F such that E necessarily happens iff F does, but one can still intend E without intending F, even if one knows about the equivalence (mere knowledge does not change one's intentions).